Electromagnetic Field Probe for Microwave Ovens

This paper proposes a probe to monitor the electromagnetic field inside the microwave oven. Although magnetrons are now small and efficient, and solid-state ovens can control the power delivered to the food, neither can “see” the electromagnetic field inside the microwave oven. Therefore, the proposed field detector probe, which is a rectenna (antenna and rectifier), converts the RF (2.45 GHz) signal, inside the cavity, to a dc voltage. The antenna is a simple planar monopole, which is not matched due to the high power levels inside the oven. Two types of rectifiers are proposed, the first one is based on diodes (SMP1302 or SMP1304) and the second one is based on an LDMOS power transistor-BLC2425M8LS300P, provided by Ampleon. By comparing the output dc voltage of the probe when connected to a signal generator (in the laboratory) with the voltage generated by the field detector probe (inside the microwave oven), the electromagnetic field can be mapped. Doing this allows microwave oven manufacturers to optimize and adjust the cooking appliance based on the electromagnetic field, which induces food heating.